Our overriding theme is ultra high-throughput radiation biodosimetry. It is well established that this is a central and necessary component of any effective response to a large scale radiological event. The RABIT (Rapid Automated Biodosimetry Tool) system developed to date in Project 1 has a current throughput of 6,000 samples / day, and a projected (2010) throughput of 30,000 samples / day. These throughputs were achieved by complete robotically-based automation of standard micronucleus and Y-H2AX assays. One first main renewal theme, "Beyond Simple Exposures", is to assess the significance of various realistic radiation event scenarios, in particular protraction of radiation exposure, partial-body exposure, internal emitters, and neutron exposure. Our goal is to understand the responses of the standard RABIT assays to these types of exposures, and quantify the uncertainties associated with dose reconstruction in these scenarios. The assays will be done both with irradiated mice and with ex-vivo irradiated human blood, with the unique irradiation facilities of the Irradiation Core, allowing sample sharing with the other two Projects. While the micronucleus assay has high throughput and excellent post-irradiation stability, its assay time is ~3 days, due to the need to stimulate cell division in vitro. We have preliminary evidence of the practicality of a micronucleus assay using /T?ononi;c/ear lymphocytes, which have already divided in vivo. Our second theme is to develop and assess this system which, with full automation, would reduce the assay time to ~3 hrs Having developed high-throughput systems using various biomarkers for biodosimetry, we are in a unique position to probe the application of these high-throughput biomarkers for predicting inter-individual sensitivity to acute radiation injury. Thus our final renewal theme is "Beyond Dose: Towards Individual Radiosensitivity". The six high-throughput automated RABIT endpoints that we will use are baseline micronuclei, ex-vivo radiation-induced micronuclei, ex-vivo radiation-induced y-H2AX, ex-vivo radiation-induced chromosomal deletions, DNA damage repair kinetics (with Y-H2AX, ATM, 53BP1, and Mdcl foci), and residual damage after 24 h. The practical use of this number of assays is made possible by their being fully automated within the RABIT. Studies will be done with inbred mice with differing acute radiosensitivities, and by assessing associations between these endpoints and acute erythema in 500 irradiated breast cancer patients.